1. Field of the Invention
The present invention relates to a power supply apparatus which is capable of performing a precharging process for preventing a relay circuit from being damaged by an inrush current, and a method of controlling such a power supply apparatus.
2. Description of the Related Art
There is known a power supply apparatus having a high-voltage battery for use on vehicles or the like {see Japanese Laid-Open Patent Publication No. 2001-327001 (hereinafter referred to as “JP2001-327001A”)}. According to JP2001-327001A, two system main relays (SMR1, SMR2) are connected in parallel to each other between battery modules (BM1, BM2) of an HV battery (194) and a drive circuit (191, 192) and a motor (MG1, MG2) (see FIG. 2 of JP2001-327001A). A limiting resistor (LR) is connected in series to one of the system main relays (SMR1).
For energizing the motors, firstly the system main relay (SMR1) is turned on to perform a precharging process. Since the limiting resistor (LR) is connected to the system main relay (SMR1), a load voltage (Vinv) increases gradually to prevent an inrush current from being generated (FIG. 3 and paragraph [0049] of JP2001-327001A). When the load voltage (Vinv) reaches about 80% of a power supply voltage (Vbat), for example, the precharging process is completed, and the other system main relay SMR2 is turned on. When the load voltage (Vinv) becomes substantially equal to the power supply voltage (Vbat), the system main relay (SMR1) is turned off, thereby bringing the HV battery (194) into an ON state (paragraph [0049] of JP2001-327001A).